Easy Sweet and Sour Chicken

Name: Easy Sweet and Sour Chicken
Prep time: 5 min
Cook time: 10 min
Total time: 15 min
Cuisine: Asian
Ingredients: 3/4 cup granulated sugar; 1/2 cup apple cider vinegar; 1/4 cup ketchup; 2 tablespoons low-sodium soy sauce; 1 tablespoon sesame oil; 1 tablespoon light brown sugar, packed; 3 cloves garlic, pressed or finely minced; 2 tablespoons cold water; 1 tablespoon cornstarch; about 1.25 pounds boneless skinless chicken breasts, cut into 1-inch pieces; 3 tablespoons cornstarch; salt and pepper, to taste; 3 to 4 tablespoons olive oil, plus more if necessary; 2 green onions, sliced into thin rounds, optional for garnishing; 1 tablespoon sesame seeds, optional for garnishing